The Yojo (Protection) Pattern — Stop Your AI Coder from Wasting Time and Tokens

TL;DR When changing designs, hide old design and old code from your AI coder's eye before you start implementation. Don't instruct it to "ignore the old design" — make sure it never sees it . Same principle as a racehorse shadow mask. 1. The Problem: An Antipattern Unique to AI Coding After 8 months of AI-assisted development, I kept hitting the same wall. Every design change triggered the same failure mode — and switching to the latest model didn't fix it. The cause wasn't model capability. It was a structural problem in context design. 1.1 What Happens When You Ask AI to Change a Design What you want: old design → new design (complete replacement) What you get: old design + new design (dual implementation) Symptoms: Unnecessary backward-compatibility layers ("I'll keep the old API just in case") Dual implementations (old and new processing coexist) Old design remnants left behind (old fields, old classes persist) Excessive warnings and foot-dragging ("This is a Breaking Change") This